Printing machine with rotatable stencils and automatic ink supply



Feb. 15, 1944. R. KORESKA 2,341,627

PRINTING MACHINE WITH ROTATABLE STENCILS AND AUTOMATIC INK SUPPLY I Filed Jan. 8. 1940 Patented Feb. 15, 1944 UNITED STATES PATENT OFFICE PRINTING MACHINE WITH ROTATABLE STENCILS AND AUTOMATIC INK SUPPLY Application January 8, 1940, Serial No. 312,962 In Germany December 1, 1938 6 Claims. (Cl. 101-122) For the production of clean and uniform copies by means of printing machines with rotatable stencils the correct inking of the stencils is especially important. Too little ink results in weak copies, too much ink results in visible oil shadows, soaking of ink through the paper to the rear side of the copy, fringed characters and possibility of easily becoming blurred.

The inking was efiectecl in two-drum printing machines up to the present in such a manner that from time to time ink was added arbitrarily by hand. Herefrom results at first an excess in ink which soon becomes a deficiency of ink, especially when large continuous surfaces giving 01f ink are employed. The copies from one and the same stencil are thus often unequally inked. This irregularity can, however, occur on each copy, for instance with stencils which irregularly consume ink over their width, for which case an additional inking at certain points of the stencils is necessary.

To overcome these inconveniences apparatuses have been built with ink-supply effected permanently or intermittently from the drive, devices being further known which make it possible to supply ink at those points of the stencil at which the ink consumption is higher than at other points. But also these improved apparatus possess still inconveniences which are substantially as follows:

1. The quantity of ink to be automatically supplied must be adjusted and corrected after a certain number of copies have been made. This requires experience and skill and excludes rapid working.

2. The construction of such ink conveying devices is complicated and expensive, especially if the device has to supply ink to only certain portions of the drums.

3. The ink consumption is not economical owing to the still existing irregularities in inking and to the tendency of overinking.

The object of the invention is to obviate these inconveniences by simple means, i. e., and to provide a two-drum copying apparatus which, with absolutely automatical inking under economical conditions as regards consumption of ink, time and expenses for the apparatus, supplies absolutely uniform ink copies at any in consumption of the stencil surface.

With this object in view a continuous ink circulation is intended according to the invention so that ink conveying means is provided which supplies ink in a great quantity, related to the ink consumption necessary for the production of one copy, permanently to a drum circumference, means known as such being provided which remove the excess of ink from the drum, for instance, by scraping. This proceeding is new for two-drum rotation stencil copying apparatus. The proposition to work in such apparatus with comparatively large quantities of ink, but to utilize this ink only for a fraction, that is that fraction which is necessary for the production of the copies, and to remove again the excess of ink was considered up to the present as impossible for two-drum copying apparatus. This proceeding, is however, compared with what is known much more practical in that thereby notwithstanding a less great use of constructive auxiliary elements uniform copies are supplied.

Compared with the automatic devices of known type for supplying ink in two-drum copying apparatus, the ink according to the invention is supplied in comparatively considerable quantities and without the necessity to regulate the quantity accurately in accordance with the consumption in the printing mechanism, this being possible with the aid of technically simple means, because the accurate subdivision into predetermined and very small ink quantities is no longer necessary. As the ink is supplied in excess, absolutely taken in a large quantity which technically can be easily handled, also the discharge of the excess is made in larger quantities which technically can be more easily gov erned.

The intended success occurs only if all these preliminary conditions are fulfilled. The permanent automatic ink supply alone would lead to damming up the ink, whereas the automatic ink discharge without simultaneous regular admission would also lead to the disagreeable ink excess or lack of ink. For theinvention it is therefore essential to produce a continuous, regular throughflow of ink throughthe two-drum apparatus, the always existing capability of ac.- cumulating ink in the elements of the. apparatus in which the ink is contained maintaining a certain quantity of ink. If these conditions are fulfilled, the surprising effect is obtainedthat excellent copies of greatest uniformity can be obtained even if the ink consumption of a stencil considerably varies over the width of the same. This means, however, that such apparatus does not require the expensive auxiliary means for enabling the ink supply atcertain points of the stencil.

In the accompanying drawing:

Fig. 1 is an end elevational view, partly in section, of a two-drum rotary stencil printing apparatus constructed in accordance with the present invention, and

Fig. 2 is a longitudinal sectional view, partly broken away and. taken on line. 2-2 of Fig. 1.

As shown in the drawing, the reference numeral l3 designates the upper drum and M the lower drum, a stencil carrier I5 being wound around these drums. A rubbing roller is designated by Hi. An additional roller IT is pressed by means of a spring l8 against. the drum. I 3 and rotates in a vessel I9. This vessel I9 is filled with ink. If therefore the upper drum 13. revolves in the direction of the arrow a, the roller IT is positively drawn along by' friction; in. the direction of the arrow 1), so that the. ink is supplied on to the circumference of drum t3 and rubbed by the roller l6. The ink then gets from below onto the stencil carrier and inks the stencil through this. carrier.. The ink which is not consumed is brought. to in front of the roll ll which acts as damming. elements and causes the flowing off of the ink in excess;

In this form of construction of the machine the ink supply as well as the removal of. the excess ink is effected. by one single ink roller ll pressing against the: circumference of drum is. This roller, which regulates the circulating quan tity of ink, must preferably be" of less great diameter than and. bear tightly against the outer circumference of a drum.

As the roll I! allows only a predetermined quantity of ink to pass throughv between itself and the drum I3 only a: very small portion of the ink taken from the container l9 is conveyed; the larger portion of ink is dammed up in front. of the gap through which it passes and flows then back into the container; Otherwise expressed: a comparatively large quantity of ink is offered to the outer'wall. of drum l'3, but only a fraction of the same is utilized. Two or more separate devices may, however, be provided for offering the ink and for removing the excessof ink. With this object in view the roll llmust be strongly pressed against the drum- 1-3;

If the quantity of ink, which has to: pass throughv between the roll IT and: drum l3, has to ing the roll of a larger diameter or thereby that, by giving to the auxiliary roller. I1: a certain cross-section, the gap is enlarged, which in total-results in a certain passage cross-section.

Also the pressure at which the roller I1 is pressed against the drum l2- influences the circulating ink quantity.

The. space which serves for accommodating the ink container l9 (Fig. 2)- is restricted. The container H) can be lengthened in outward direction and widened to a trough. As it has been found to be suitable to leave the inkv in container I9 always at the same level, a tank 21 for ink or any other ink dischargev pipe may clip with its downwardly directed discharge aperture into the trough so that according to the well known physical principle, the height of the ink level in the trough remains always the same.

Evidently the invention may be applied, in.- stead of to two-drum apparatus; to multi-drum apparatus, such as three-drum apparatus without departing from the spiritof the invention.

I claim:

1. A rotary two-drum stencil printing apparatus including two drums, an endless stencil carrier, said carrier enclosing and moving over both drums, and an ink roller arranged below and in contact with the outer wall of one of said drums, for continuously inking the said outer wall so as to maintain automatically an ink layer of constant thickness thereon and holding in circulation a quantity of ink which is large as compared with the ink consumed at the production of a stencil copy.

2. A rotary two-drum stencil printing apparatus including two drums, a stencil carrier, said carrier enclosing and moving over both drums, an ink roller. arranged below and in contact with the outer wall of one of said drums, and means whereby said ink roller is pressed against said outer wall, said ink roller being arranged for continuously inking the said outer wall so as. to maintain automatically an ink layer of constant thickness thereon and holding in circulation a quantity of ink. which is large as compared with the ink consumed at the production of a stencil copy.

3. A rotary two-drum stencil printing apparatus including twov drums, an endless stencil carrier, said carrier enclosing and moving over both drums, and an ink roller arranged below and incontact with the outer wall of one of said drums so as to be positively rotated by friction by one of the said drums when the drum revolves, said ink roller being arranged for continuously holding in circulation a. quantity of ink whichis large as compared with the ink consumed at the production of a stencil copy and automatically maintainingv an ink layer of constant thickness on said outer wall.

lL'A rotary two-drum stencil printing apparatus including two drums, an endless stencil carrier, said carrier enclosing and moving over both drums, an ink roller arranged below and in contact with the outer wall of one of said drums, and an ink container wherein said ink roller is dipping, said ink roller being arranged for continuously inking the said outer wall so as to maintain automatically an ink layer of constant thickness thereon and holding in circulation a quantity of ink which is large as compared with the ink consumed at the production of a stencil copy. be altered, this may be efl'ected either by mak- 5. A rotary two-drum stencil printing apparatus including two drums, an endless stencil carrier enclosing and moving over both drums, an ink roller arranged below and in contact with the outer wall of one of said drums so as to be positively rotated by friction by said one drum when the same revolves, and an ink container surrounding the lower part of the said ink roller and being so arranged that any excess ink accumulating on the said outer wall in front of the passage between said wall and the ink roller refiows into said. ink container, said ink roller being arranged for continuously inking the said outer wall, automatically maintaining thereon an ink layer of constant thickness and holding in circulation a quantity of ink which is large as compared with the ink consumed at the production of a stencil copy.

6. A rotary two-drum stencil printing apparatus as specified in claim 2 wherein the said means. for pressing the ink roller against the outer wall of one of the drums comprises a spring device inserted between the ink roller and the drum.

ROBERT KORESKA. 

